Bearingless angular measurement device

ABSTRACT

A bearingless angular measurement device includes an angle scale, a scanning unit, and an evaluation electronics. The scanning unit and the angle scale are located at a scanning distance relative to each other and are rotatable about an axis, so that the scanning unit is capable of generating angle-dependent output signals, which may be further processed in the evaluation electronics. The scanning distance is able to be determined on the basis of the output signals. In addition, the angular measurement device includes a compensation coupling that is attachable to a machine component and is elastically deformable in the direction of the axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Application No. 10 2018 202239.9, filed in the Federal Republic of Germany on Feb. 14, 2018, whichis expressly incorporated herein in its entirety by reference thereto.

FIELD OF THE INVENTION

The present invention relates to a bearingless angular measurementdevice.

BACKGROUND INFORMATION

Angle-measuring devices may be based on an inductive, a magnetic, or acapacitive measuring principle and, for example, are used in rotaryencoders for the purpose of determining the angular position of twomachine parts that are rotatable relative to each other.

In the case of inductive angle-measuring devices, excitation coils andreceiver coils in the form of circuit traces are frequently applied on ashared circuit board as a scanning unit, the circuit board being fixedlyconnected to a stator of a rotary encoder, for example. Situated acrossfrom this circuit board is a further circuit board on which, as an anglescale, electrically conductive surfaces are applied at periodicintervals as a graduation structure, the further circuit board beingconnected to the rotor of the rotary encoder in a torsionally fixedmanner. When an electric excitation field is applied at the excitationcoils, output signals are generated in the receiver coils as a functionof the angular position during the relative rotation between the rotorand stator. These output signals are then further processed inevaluation electronics.

In principle, it is distinguished between angular measurement deviceshaving integral bearings and angular measurement devices withoutintegral bearings, hereinafter referred to as bearingless angularmeasurement devices. Angular measurement devices having integralbearings usually have relatively small rolling bearings, so that thecomponent groups that are rotatable relative to one another within theparticular angle-measuring device are situated in a defined axial andradial position relative to one another. In the case of bearinglessangular measurement devices, on the other hand, attention must be paidduring the installation on a machine that the component groups that arerotatable relative to one another are installed in the right positionand, in particular, are fixed in place at the correct axial distancefrom one another.

European Published Patent Application Nos. 1 750 101 and 1 126 248describe angular measurement devices that are suitable for determining ascanning distance.

SUMMARY

Example embodiment of the present invention provide a bearingless, e.g.,an inductive, angular measurement device so that a precise determinationof the scanning distance is possible and an optimized mechanicalconnection is obtained.

According to an example embodiment of the present invention, abearingless angular measurement device includes an angle scale, ascanning unit, and an evaluation electronics. The scanning unit and theangle scale are disposed at a scanning distance relative to each othersuch that a rotation about an axis is possible. In addition, thescanning unit is adapted to generate angle-dependent output signals,which may be further processed in the evaluation electronics. Theangular measurement device is configured such that the scanning distanceis able to be determined on the basis of the output signals.Furthermore, the angular measurement device includes a compensationcoupling, which is able to be fixed in place on a machine component andis elastically deformable in the direction of the axis.

The compensation coupling is arranged so that it pushes the angularmeasurement device, in particular the component group of the angularmeasurement device in which the scanning unit is fixed in place in atorsionally fixed manner, against the machine component on a permanentbasis.

Angle-dependent output signals, for example, include signals thatinclude information about the relative angular position between theangle scale and the scanning unit.

The compensation coupling may be elastically deformable in the directionof the axis across a travel of at least 0.5 mm, e.g., at least 1.0 mm,at least 1.5 mm, etc.

The compensation coupling may include a plurality of angled components.In this context, each of the components may have a first lateral side,which extends in a direction with a radial directional component, and asecond lateral side, which extends in a direction with an axialdirectional component.

The scanning unit may be connected to a housing in a torsionally fixedmanner, and the compensation coupling may also be fixed in place on thehousing in a torsionally fixed manner.

The compensation coupling may be torsionally stiff, e.g., such that itdoes not deform, or deforms only to an extremely limited extent, inresponse to introduced tangentially directed forces. In addition, thecompensation coupling may have a rigid configuration with regard to aradial direction.

The angular measurement device may be arranged as an inductive angularmeasurement device.

The scanning unit may be adapted to scan the angle scale across at leastone half of its circumference, thereby making it possible to generateangle-dependent output signals. The scanning unit may be able to scanthe angle scale across at least 66%, e.g., across 75% of thecircumference. In particular, the angular measurement device may beconfigured so that the inclination of the axis relative to the scanningunit is able to be determined on the basis of the output signals.

An inductive angular measurement device may be configured such that theangle scale is scannable by the scanning unit or by the sensor coilsacross a large portion of its circumference, thereby making it possibleto generate angle-dependent output signals. Alternatively, the angularmeasurement device may be configured such that the angle scale isscanned via a plurality of scanning points distributed across thecircumference, so that the inclination of axis X is able to bedetermined in such a manner.

The evaluation electronics may include a unit adapted to determine thesignal amplitudes of the output signals, and the scanning distance isable to be determined on the basis of the signal amplitudes of theoutput signals.

The unit adapted to determine the signal amplitudes may be allocated toa control unit, which is configured such that by acting on a controlvariable, the signal amplitudes of the output signals do not exceed apredefined deviation from a setpoint amplitude value.

The angular measurement device may include an electronics system bywhich the scanning distance is able to be determined. In particular, theevaluation electronics may be adapted to determine the scanningdistance. Via a digital interface, for example, the scanning distancemay be transmitted to an external (relative to the angular measurementdevice) subsequent electronics for the further electronic processing.Alternatively, the determined scanning distance may be further processedelectronically within the angular measurement device. The determined orcalculated scanning distance is thus used for the further electronicprocessing inside or outside the angular measurement device.

The evaluation electronics may be adapted to generate a digital valuefor the scanning distance, e.g., a binary number, which may be furtherprocessed in a microprocessor. If this microprocessor is situatedoutside the angular measurement device, then the angular measurementdevice may include an interface by which the value is transmittable to asubsequent electronics.

Further features and aspects of example embodiments of the presentinvention are described in greater detail below with reference to theappended Figures.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross-sectional view of an angular measurement device.

FIG. 2 is a first perspective view of the angular measurement device.

FIG. 3 is a second perspective view of the angular measurement device.

DETAILED DESCRIPTION

An angular measurement device according to an exemplary embodiment ofthe present invention, which is arranged as an inductive angularmeasurement device, for example, is illustrated in FIGS. 1 to 3. Theangular measurement device includes a first component group 1 and asecond component group 2, the two component groups 1, 2 being arrangedso as to be rotatable relative to each other about an axis X. To ensurethe relative rotatability, no integral bearing, i.e., no rolling bearingor sliding bearing, is provided in the angular measurement device(bearingless angular measurement device). Instead, first component group1 is attached to a first machine component, and second component group 2is attached to a second machine component. The first machine componentis arranged so as to be rotatable relative to the second machinecomponent. Component groups 1, 2 lie across from each other and areseparated by an air gap.

In the illustrated exemplary embodiment, first component group 1 of theangular measurement device has a shaft 1.1, which has a conical end forthe rigid and torsionally fixed attachment to a machine or a motorshaft. Accordingly, shaft 1.1 has a convex mounting area 1.11. An anglescale 1.2 is fixed in place on shaft 1.1 and includes an annular circuitboard on which conductive and non-conductive regions, i.e., regionshaving different electrical conductivities, are provided in a periodicsequence and at identical graduation steps. First component group 1 ofthe angular measurement device may also be referred to as a rotor.

A scanning unit 2.2, which is allocated to second component group 2,which may also be referred to as a stator in this case, is disposedacross from angle scale 1.2 at a scanning distance D. Scanning unit 2.2is provided in the form of an annular circuit board, which includesexcitation coils and sensor coils. Furthermore, scanning unit 2.2 isattached to a housing 2.3. In addition, components of an evaluationelectronics 2.21 are provided inside housing 2.3. An ASIC component, forexample, is allocated to evaluation electronics 2.21. Integrated intothis ASIC component is a circuit for determining the relative angularposition between scanning unit 2.2 and angle scale 1.2, as well as acontrol unit. Moreover, a plug connector 2.22 to which a connectioncable to a subsequent electronics is connectable is provided in housing2.3.

Housing 2.3 is connected to a compensation coupling 2.1 in a torsionallyfixed manner. In the illustrated exemplary embodiment, compensationcoupling 2.1 includes four components 2.11 as well as a flange 2.12.Components 2.11 are produced from sheet metal and have an angled form ineach case, which means that components 2.11 have a first lateral part2.111 and a second lateral part 2.112. First lateral parts 2.111 extendin a direction with a radial directional component, and second lateralparts 2.112 extend in a direction with an axial directional component ineach case, in particular parallel to axis X. In the illustratedexemplary embodiment, first lateral parts 2.111 are attached to housing2.3 and second lateral parts 2.112 are attached to flange 2.12.Components 2.11 are constructed such that compensation coupling 2.1 iselastically deformable in the direction of axis X. In the illustratedexemplary embodiment, compensation coupling 2.1 is deformed merelyelastically, even at an axial travel of, e.g., 1.0 mm, and assumes theoriginal position again when the deflection force is removed.

In addition, compensation coupling 2.1 is torsionally stiff and radiallystiff.

Angle scale 1.2 and scanning unit 2.2 are rotatable relative to eachother, angle scale 1.2, attached to shaft 1.1, rotating during theoperation of the angular measurement device. In this case, the relativerotational speed between scanning unit 2.2 and angle scale 1.2 thus alsocorresponds to the rotational speed between shaft 1.1 and stationaryhousing 2.3 or flange 2.12. Because of the non-rotating excitation coilson the scanning unit 2.2 on the stator side, a homogeneous alternatingfield is generated during the operation of the angular measurementdevice, which is modulated by angle scale 1.2 as a function of theangular position or of the angle of rotation of shaft 1.1. In the sensorcoils, which are likewise situated on scanning unit 2.2, angle-dependentoutput signals are generated by the modulated electromagnetic field.

In the illustrated exemplary embodiment, the angular measurement deviceis configured for all-round scanning. In other words, scanning unit 2.2is particularly configured so that angle scale 1.2 is able to be scannedby scanning unit 2.2 or by the sensor coils virtually across the entirecircumference and so that angle-dependent output signals are able to begenerated in this manner. In other words, scanning unit 2.2 scansvirtually the entire graduation structure of angle scale 1.2 in order toobtain a position signal.

The output signals generated in the process are forwarded to evaluationelectronics 2.21 where they are further processed. In the control unit,the output signals are controlled to the effect that they have unchangedsignal amplitudes or levels at all times. Toward this end, the signalamplitudes of the output signals are first determined as instantaneousvalues. Then, the deviation is determined between the previouslydetermined signal amplitudes and a predefined setpoint-amplitude value.Depending on the amount of the deviation, a control variable isascertained with the goal of keeping the deviation within predefinedlimits. By influencing this control variable, which is the energizationof the transmit coils in the illustrated exemplary embodiment, thesignal amplitudes are largely kept at a constant level.

For example, the angular measurement device may be used in conjunctionwith a brake of an electric motor. In this case, compensation coupling2.1 or flange 2.12 of compensation coupling 2.1 may be mounted on thesecond machine component. The second machine component may be a brakepad, for instance. Compensation coupling 2.1 is also used for the axialspring-loading or for the generation of an axial contact pressure thatpermanently forces housing 2.3 against the second machine component,regardless of whether or not the brake has been applied. Shaft 1.1 ispermanently connected to the motor shaft. The brake in such systems isnormally used as a holding brake and is not engaged when the motor shaftis rotating.

If the brake is applied, housing 2.3 moves in direction ξ (see FIG. 1).First component group 1, on the other hand, remains in an unchangedaxial position. This causes a deformation of components 2.11 ofcompensation coupling 2.1, which are elastic in the axial direction;more specifically, first lateral sides 2.111 move out of the plane ofthe ring of flange 2.12 in the region of the bending edge. At the sametime, scanning distance D becomes smaller.

To begin with, the actual instantaneous value of scanning distance D isdetermined while the angular measurement device is in operation. Forthis purpose, the output signals, which are incremental signals in thiscase and offset in phase by 90°, are conveyed from scanning unit 2.2 toevaluation electronics 2.21. In the control unit, an amount of thecontrol variable required for controlling the signal amplitudes thatremain constant is formed. In the illustrated exemplary embodiment, thesignal amplitudes are determined in the unit by forming an amplitudemean value from eight consecutive output signals in each case. It isthen checked to what extent the signal amplitudes thereby determineddeviate from a predefined setpoint-amplitude value. If the amount of thedeviation is too large, or if the signal amplitudes lie outside apredefined control window, then the amount of the control variable orthe amplification factor will be modified accordingly, so that thelevels or the signal amplitudes of the output signals come closer to thesetpoint amplitude value.

In addition, the angular position, or position values, of shaft 1.1 isdetermined in the circuit on the basis of the output signals.

As a matter of principle, it may be determined that the amount of thecontrol variable or the amplification factor or the energization of thetransmit coils increases as actual scanning distance D becomes larger.

Scanning distance D consequently includes the information as to whetheror not the brake is activated. As a result, it is possible to firstascertain the respective current state of the brake (activated orunengaged) in the above-described manner.

In addition, the wear state of the brake is able to be detected due tothe exact determination of scanning distance D. In the illustratedexemplary embodiment, the amount of the control variable or theamplification factor is monitored on a continuous basis. If a slowchange occurs in this variable, it may be assumed that this change wasnot triggered by an activation of the brake but by other influences suchas a change in the temperature in the angular measurement device. In thecase of a rapid change in the amount of the control variable or theamplification factor, on the other hand, a braking operation may beinferred. In such a case, the change in scanning distance D is measuredfrom the start of the occurrence of a particular gradient of scanningdistance D to the end of the corresponding movement. The greater thewear of the brake, the greater the change in scanning distance D due toa braking operation. This allows for a precise determination of thebrake wear to, e.g., 0.1 mm so that a statement is possible regardingthe remaining service life of the brake.

Such brakes are frequently also constructed such that two brake pads areprovided for reasons of a required redundancy, which, situated acrossfrom each other, engage on one side of axis X in each case. If unevenwear is present, however, it may happen that the activation of the brakecauses tilting of axis X relative to housing 2.3 or relative to scanningunit 2.2. Since scanning unit 2.2 is arranged such that angle scale 1.2is scannable by scanning unit 2.2 or by the sensor coils virtuallyacross the entire circumference (all-round scanning), the output signalsmay be exploited for determining the inclination of axis X. Accordingly,in the illustrated exemplary embodiment, the angular measurement deviceis configured so that the inclination of axis X relative to scanningunit 2.2 is able to be determined on the basis of the output signals.The extent of the inclination, or the angle of inclination, thusprovides information about the state or the position of the brake, inparticular about the uniformity of the wear of two brake pads.

As a result, it is possible to use the angular measurement device todetermine whether or not the brake is engaged. In addition, a defect,e.g., resulting from an excessive degree of the afore-describedinclination, may be detected. Moreover, due to the measuring accuracythat is provided in this instance, the wear state of the brake isascertainable as well. This requires no separate position-measuringdevice either for determining scanning distance D or for determining theinclination of axis X.

Depending on the respective requirements, either scanning distance D orthe inclination of axis X, or both variables, is/are able to betransmitted to the subsequent electronics via an interface which isprovided on the angular measurement device, using a serial datatransmission, for example. In addition, the angular position and therotational speed of shaft 1.1 are also forwarded to subsequentelectronics for further electronic processing.

What is claimed is:
 1. A bearingless angular measurement device,comprising: an angle scale; a scanning unit; a compensation coupling;and an evaluation electronics; wherein the scanning unit and the anglescale are located at a scanning distance relative to each other and arerotatable relative to each other about an axis; wherein the scanningunit is adapted to generate angle-dependent output signals, theevaluation electronics adapted to process the output signals, theangular measurement device adapted to determine the scanning distancebased on the output signals; wherein the compensation coupling isattachable to a machine component and is elastically deformable in adirection of the axis; wherein the machine component includes a brakepad of a brake of an electric motor; and wherein an activation state ofthe brake is ascertainable based on the determined scanning distanceand/or a wear state of the brake is determinable based on the determinedscanning distance.
 2. The bearingless angular measurement deviceaccording to claim 1, wherein the compensation coupling is elasticallydeformable in the direction of the axis by at least 0.5 mm.
 3. Thebearingless angular measurement device according to claim 1, wherein thecompensation coupling includes a plurality of angled components.
 4. Thebearingless angular measurement device according to claim 3, whereineach component includes a first lateral side extending in a directionwith a radial directional component, and a second lateral side extendingin a direction with an axial directional component.
 5. The bearinglessangular measurement device according to claim 1, further comprising ahousing, the scanning unit being connected to the housing in atorsionally-fixed manner, the compensation coupling being fixed in placeon the housing in a torsionally fixed manner.
 6. The bearingless angularmeasurement device according to claim 1, wherein the compensationcoupling is torsionally stiff.
 7. The bearingless angular measurementdevice according to claim 1, wherein the angular measurement device isarranged as an inductive angular measurement device.
 8. The bearinglessangular measurement device according to claim 1, wherein the scanningunit is adapted to scan the angle scale across at least one half of acircumference of the angle scale to generate angle-dependent outputsignals.
 9. The bearingless angular measurement device according toclaim 8, wherein the angular measurement device is adapted to determinean inclination of the axis relative to the scanning unit based on theoutput signals.
 10. The bearingless angular measurement device accordingto claim 1, wherein the evaluation electronics includes a unit adaptedto determine the signal amplitudes of the output signals, the scanningdistance being determinable based on the signal amplitudes of the outputsignals.
 11. The bearingless angular measurement device according toclaim 1, wherein the angle scale is arranged on a shaft adapted toattach to a machine and/or a motor shaft.
 12. The bearingless angularmeasurement device according to claim 1, wherein the scanning unitincludes an annular circuit board.
 13. The bearingless angularmeasurement device according to claim 4, wherein the compensationcoupling includes a flange, the second lateral side of each componentbeing attached to the flange.
 14. The bearingless angular measurementdevice according to claim 4, further comprising a housing, the scanningunit being connected to the housing in a torsionally-fixed manner, thecompensation coupling being fixed in place on the housing in atorsionally fixed manner, the first lateral side of each component beingattached to the housing.
 15. The bearingless angular measurement deviceaccording to claim 12, wherein the annular circuit board includesexcitation coils and sensor coils.
 16. The bearingless angularmeasurement device according to claim 15, wherein the excitation coilsare adapted to generate an electromagnetic field, the angle scale isadapted to modulate the electromagnetic field, and the sensor coils areaadapted to generate the angle-dependent output signals based on themodulated electromagnetic field.
 17. The bearingless angular measurementdevice according to claim 1, wherein the scanning distance between thescanning unit and the angle scale is changeable based on the elasticdeformation of the compensation coupling.
 18. The bearingless angularmeasurement device according to claim 1, wherein the scanning distancebetween the scanning unit and the angle scale is changeable during ameasurement operation of the angular measurement device based on theelastic deformation of the compensation coupling.